Improvement of quality and yield for investment casting of centrifugal pump impeller by tilting mold and optimizing runner/riser system

Abstract

Abstract The impellers must have no defects to endure vibration and centrifugal force. The shell for producing impeller was located at tilt and the runner/riser system was optimized to obtain good quality casting and increase the casting yield. We adopted sprue as riser to increase the casting yield and employed ProCAST to analyze the solidification behavior of molten metal according to the dimension of riser and gate. Although the diameter of riser is change from 133mm to 66mm, the shrinkage defects was removed from the casting due to the proper size and location of runner/riser system. And we predicted the probability occurring gas and non-metal inclusion defects in casting by tilting the shell at 0°, 5°, 10°, 15° and 20°. The ultrasonic detecting results show that the proper designs of the runner/riser systems and mold tiling eliminated casting defects such as shrinkage, gas and non-metal inclusion. In addition, the casting yield was increased from 41.5 to 65.2% with producing a good quality casting.